Sailing Master Able Six, Royal Navy, is a man like no other.

To call him a mere polymath is to sell him short. Someone with his extraordinary gifts should rise to the top, unless it is the 1800s, where pedigree and money govern Regency society, as sure as Napoleon seeks world domination. A bastard raised in a Scottish workhouse with nothing in his favor except his amazing mind, Able must navigate life ashore on half-pay during the uneasy Truce of Amiens, and find a way to provide for his charming bride Meridee Bonfort, a gentlewoman to be sure, but lacking a dowry.

Assisted by two sea captains acquainted with his startling abilities, Able finds himself teaching mathematics and seamanship at St. Brendan the Navigator School, which is itself an experiment, taking boys like Able from workhouses and training them to serve the fleet in wartime. Meridee has agreed to invite four lads who need extra attention into their home in raffish, unsavory Portsmouth.

Calling themselves the Gunwharf Rats, these St. Brendan lads show promise in an unpromising world. Can a sailing master-turned-teacher uncover their potential? Can Meridee find a way to nurture young hearts bruised too soon by life? What will happen when war breaks out again? And what is it about Able Six, the unlikely master genius?